1. Field of the Invention
The present invention relates to a semiconductor laser light source designed to integrate a plurality of laser beams, and a solid-state laser apparatus using the same.
2. Description of the Related Art
A semiconductor laser, which is small in size, highly reliable, and easy to maintain as compared with a gas laser, a solid-state laser or the like, is widely used in the optical communication field, optical disk devices and so on. However, the semiconductor laser is still under development in fields which require high-output laser beams such as laser welding and laser scalpel field. The optical output obtained from one semiconductor laser is limited to approximately several milliwatts to several hundreds of milliwatts in CW (constant wave) operation. It is thus quite difficult to apply the semiconductor laser to the aforementioned fields. To deal with this problem, it has been researched to increase the output of laser beam by integrating laser beams from a plurality of semiconductor lasers.
On the other hand, since the laser beam of the semiconductor laser has a great divergent angle, high accuracy is required for the configuration and arrangement of optical elements, so that it is technically quite difficult to integrate a plurality of laser beams. However, in the case where it is made possible that a plurality of laser beams are joined, for example, to one optical fiber, the application range of the semiconductor laser will increase.
As prior art, Japanese Unexamined Patent Publication JP-A 60-76707 (1985) discloses a semiconductor laser duplex module for optical communication, directed to improve the reliability by multiplexing with the following features. An optical system is used which, in order that beams from two semiconductor lasers are caused to enter one optical fiber, rotates the polarization plane of one laser beam 90 degrees and then merges the two laser beams by the birefringence effect, and when one suffers a breakdown, the other continues operation.
However, in the arrangement of JP-A 60-76707, when a semiconductor laser having a great divergent angle is used, since the incident angle on the birefringent element greatly differs between the light in the vicinity of the optical axis and the light diverging outward, the birefringence effect is not uniform, with the result that it is difficult to merge the laser beams. In addition, since the wave fronts of the laser beams are disturbed due to the large variation in the incident angle, it is difficult to converge the beams onto an optical fiber having a small core diameter.
In a semiconductor laser for optical communication which places emphasis on wave length stability and longevity, the above problem does not arise because the divergent angle is not very great. However, in a semiconductor laser for processing which places emphasis on high output and high intensity, the above problem arises because the divergent angle is generally great.
Furthermore, in the prior art, since the optical element for merging the laser beams and the optical element for joining the laser beams to the optical fiber are separately provided, the passage loss of light increases and the overall structure is complicated and increased in size, with the result that the reliability and the productivity decrease.